1. Field of the Invention
The present invention relates generally to a method for generating a frame, and in particular, to a method for generating a frame in an Orthogonal Frequency Division Multiple Access (OFDMA) communication system.
2. Description of the Related Art
Next-generation mobile communications need high-speed and high-quality data transmission to support various multimedia services of greater quality. Research is being conducted on OFDMA scheme as the scheme for satisfying this need.
Orthogonal Frequency Division Multiplexing (OFDM) scheme corresponding to a basis of the OFDMA is being widely used as a physical layer transmission scheme for various wireless communication systems such as a wireless Local Area Network (LAN), a digital Television (TV), a next-generation mobile communication system, and so on, because there are advantages in that the OFDM enables high-speed communication at low equalization complexity in a frequency selective fading channel.
As one of broadband wireless communication standards developed by the Institute for Electrical and Electronics Engineers (IEEE) working group, the IEEE 802.16 standard was approved on December 2001, under condition that a fixed point-to-point broadband wireless system operates in a spectral band of 10˜66 GHz. In the IEEE 802.16a standard as an amendment of the IEEE 802.16 approved on January 2003, an extension for non-line-of-sight in a spectral band of 2˜11 GHz is specified such that transmission can be performed within a maximum distance of 50 Km at a rate of 70 Mbps.
In addition to the IEEE 802.16 standard, various schemes are being discussed to support a high data rate in an OFDMA scheme-based wireless communication system. These various technologies are mostly related to a mechanism for allocating a dynamic frequency of a subchannel or subcarrier and power resources. For the resource allocation, correct channel information is necessary and an indication of concrete allocation information is mandatory.
FIG. 1 illustrates a radio frame structure of an IEEE 802.16 communication system. A conventional radio frame includes downlink and uplink frames. The downlink frame starts from a preamble for a downlink transmission and synchronization, and is configured by a data field, a Downlink MAP (DL-MAP) message for providing resource allocation information on a user terminal-by-user terminal basis, control information of a Uplink MAP (UL-MAP) message, and so on.
A DL-MAP message contained in the downlink frame includes common information such as a management message type, PHY synchronization Field, Downlink Channel Descriptor (DCD) count, and base station Identifier (ID) and a Downlink MAP information element (DL-MAP_E) relative to each user terminal. The DL-MAP_IE includes information about subchannels for each PHY burst of data, OFDM symbols, and Downlink Interval Usage Codes (DIUCs), and is used to define a downlink transmission.
A UL MAP message contained in the downlink frame includes common information such as a management message type, uplink channel ID, Uplink Channel Descriptor (UCD) count, allocation start time, and so on, as well as an Uplink MAP information element (UL-MAP_IE) relative to each user terminal. The UL-MAP_IE includes a Connection Identifier (CID) and an Uplink Interval Usage Code (UIUC), and it is used to define an uplink transmission.
As described above, the DL-MAP message and the UL-MAP message configuring the conventional radio frame include not only various IDs for user terminal identification and connection identification for a data transmission, but also necessary information of each of user terminal or burst. However, the DL-MAP message and the UL-MAP message are broadcasting message, so user terminal-by-user terminal or burst-by-burst information is broadcast through DL and UL-MAP messages, a waste of resources can occur.
Furthermore, because the number of DL-MAP_IEs increases proportionally to the number of bursts configuring data and the number of UL-MAP—IEs increases proportionally to the number of user terminals, user terminal-by-user terminal or burst-by-burst information is broadcast to all user terminals. For this reason, there is a problem in that there is a waste of resources.